When returning into the atmosphere, a vehicle, such as a probe, capsule inhabited vehicle, etc., needs to confront the intense heat flows and consequently the most exposed portions need to be heat-protected.
To combat the heat flows, thermic insulating materials, known as ablative materials, are used to coat the structures to be protected and whose gradual destruction under the action of the heat flow impelled by a re-entry into the atmosphere protects the coated structure from the heat by means of various mechanisms summed up as follows:
storage of energy resulting in a rise of the internal temperature of the ablative material; PA1 endothermic reaction, namely : depolymerization, fusion, sublimation, vaporization; PA1 energy loss via radiation; PA1 flow of gaseous substances opposing the heat flow.
This protection via the destruction of the thermic insulant is one of the most effective means available to combat the intense heat flows produced by an atmospheric return.
This type of material, known for a large number of years, is formed of an elastomer and/or a silicon resin. There is a RTV (Room Temperature Vulcanization) type elastomer loaded with organic components (carbonated compounds, cork) or inorganic (SiC, silica, aluminium).
This material is used as such and placed in the form of panels or mounted elements, especially glued elements, onto the surface to be protected.
So as to prevent a possible flowing of the ablative material under the heat flow, the constitutive matrix of the material, composed, for example, of a RTV elastomer, silica ecospheres and phenolic microballoons and/or other loads, is inserted in a honeycomb type structure.
Thus, it is possible to embody light, flat and mechanically resistant coating panels offering heat protection and good refractory properties.
Furthermore, by using honeycomb structures being flexible in various directions; it is possible to embody bent structures.
This technique consists of preparing the honeycomb structure, for example by indenting the walls of the cells so that the structure can be bent, followed by lining the cells of a siliconed matrix with a suitable formulation, of compacting the matrix and then shaping the entire unit in a press.
However, the flexibility of this honeycomb structure has limits concerning the degree of bending of the panels able to be made according to this technique which moreover poses the problem of filling which needs to be thorough without having any vacuum in the cells of the honeycomb structure.
Finally, the reinforcement constituted by this structure needs to be homogeneous concerning the entire weight of the final panel which does not make it possible to differentially reinforce the panel according to its various portions. For example, as it concerns a leading edge panel, it is not possible to significantly reinforce the most exposed portions of the panel, the reinforcement technique, as described earlier, proceeding by all or nothing.